Currently, there is a numerical control apparatus with which a user can cause, by designating a tool from a machining program, a machine tool to perform machining while performing replacement of the tool for each of types of machining. A series of operations for replacing the tool includes movement of a position where the tool replacement is possible, replacement of the tool, and movement to a position where the machining is started. The time required for the series of operations for replacing the tool (a tool replacement time) is the time during which a work is not machined. In the case of machining in which replacement of a tool is frequently performed, the tool replacement time greatly affects a machining time. Therefore, a reduction in the tool replacement time is desired.
On the other hand, Patent Literature 1 discloses a technology for pre-fetching a machining program and, when the next command of a tool replacement command is a positioning command, causing a tool replacing operation and a positioning operation to operate in parallel to effectively use a tool replacement time.